The present invention relates to a method of manufacturing a liquid crystal display device and, more particularly, to a method of manufacturing a liquid crystal display device called In-Plane Switching Mode.
A liquid crystal display device which is called “IPS mode (In-Plane Switching Mode)” has a construction in which a pixel electrode and a counter electrode which causes an electric field (a lateral electric field) parallel to transparent substrates to be generated between the counter electrode and the pixel electrode are formed in each pixel on the liquid-crystal-side surface of one of the transparent substrates disposed to oppose each other with a liquid crystal interposed therebetween.
The in-plane switching mode of liquid crystal display device is constructed so that the amount of light to be transmitted through the area between the pixel electrode and the counter electrode is controlled by the driving of the liquid crystal to which the electric field is applied.
Such a liquid crystal display device is known as a type which is superior in so-called wide viewing angle characteristics which enable a displayed picture to remain unchanged even when its display surface is observed from an oblique direction.
The pixel electrode and the counter electrode have so far been formed of a conductive layer which does not transmit light therethrough.
In recent years, a liquid crystal display device constructed in the following manner has been known: a counter electrode made of a transparent electrode is formed over the entire area of each pixel area except the periphery thereof, and stripe-shaped pixel electrodes made of transparent electrodes disposed to be extended in one direction and to be juxtaposed in a direction transverse to the one direction are formed over the counter electrode with an insulating film interposed therebetween.
The liquid crystal display device having this construction causes a lateral electric field to be generated between each pixel electrode and the corresponding counter electrode, and is still superior in wide viewing angle characteristics and is greatly improved in aperture ratio.
Incidentally, this art is described, for example, in SID (Society for Information Display) 99 DIGEST: pp. 202-205, or Japanese Patent Laid-Open No. 202356/1999. However, in the case where such in-plane switch mode is applied to an active matrix type of liquid crystal display device, the number of manufacturing steps, particularly, since the number of times of repetition of selective etching using a photolithographic technique reaches seven, it has been desired to decrease the number.
Since such a series of photolithographic techniques employs different photomasks for its respective photolithographic cycles, the positional deviation of the photomasks precludes the formation of a high-resolution pixel structure, and a complicated process cannot be avoided.